Design a load balancer that distributes traffic across a fleet of backend servers.

Looks simple until the follow-ups: which layer do you balance at, how do you avoid sending traffic to a dead server, and how is the load balancer itself not a single point of failure? Interviewers want the algorithm, the health-check loop, and the high-availability story.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.